1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly relates to a semiconductor device having a cylindrical lower electrode of a capacitor within a memory, and a manufacturing method of the semiconductor device.
2. Description of Related Art
Along with the development of downscaling of semiconductor devices, an area of a memory cell constituting a DRAM (Dynamic Random Access Memory) element is downsized. Therefore, an occupied area of a capacitor constituting the memory cell is limited, and securing of an electrostatic capacitance proportionate to an electrode area becomes difficult.
Regarding this problem, to sufficiently secure an electrode area, a technique of three-dimensionally forming a capacitor has been known (see, for example, Japanese Patent Application Laid-open Nos. 2003-297952 and 2003-142605). According to this conventional technique, a lower electrode of a capacitor is formed in a cylindrical shape, and an upper electrode is arranged at outside of the lower electrode via an insulator. With this arrangement, a sufficient electrode area can be secured in a small occupied area.
A step of manufacturing a capacitor includes formation of a lower electrode on an internal wall of openings formed in an insulator, removing of the insulator, and exposing of an external wall of the lower electrode. In this case, because of absence of a material that supports the lower electrode, there sometimes occurs a phenomenon (collapse phenomenon) that the lower electrode is broken and is contacted to a lower electrode of other adjacent capacitors, thereby causing short-circuit. Particularly, when an internal diameter of a lower electrode is made small to decrease the area of a memory cell or when a height of a lower electrode is increased to secure the electrode area, the collapse phenomenon occurs easily. In Japanese Patent Application Laid-open Nos. 2003-297952 and 2003-142605, to suppress the occurrence of the collapse phenomenon, a supporting film is arranged between the adjacent lower electrodes.
However, according to the above conventional supporting film, particularly when the lower electrode has a certain height or a larger height, connection strength between a buried portion and a supporting portion becomes insufficient, and thus the effect of suppressing the occurrence of the collapse phenomenon cannot be sufficiently achieved. That is, at the time of etching to remove the insulation film, the supporting film is also gradually etched, instead of not being etched at all. Therefore, the connection strength becomes weak. Further, because it takes a long etching time when the lower electrode becomes higher, the connection strength becomes conspicuously weaker as the lower electrode becomes higher.
Therefore, there has been a demand for a technique for sufficiently achieving suppression of the occurrence of the collapse phenomenon even when the height of a lower electrode is increased.